The current levels of global debt are concerning and demand action from policymakers, the former president of the European Central Bank (ECB) told CNBC on Wednesday.

"Despite the fact that real growth is active, I wouldn't say buoyant, but very satisfactory, we have some indicators on global leverage that are not that reassuring, in particular when you compute the debt outstanding, public and private, over the consolidated growth rate of the planet," Jean-Claude Trichet said at the sidelines of the Euro Finance conference in Frankfurt, Germany.

"We are now at a level which is higher than immediately before the financial crisis, so there's no time for complacency," Trichet added.

In October, the International Monetary Fund (IMF) warned governments about a record $152 trillion in global debt. At the time, the Fund said that the debt was still rising and demanded action to prevent the onset of a new financial crisis.

According to the IMF's forecasts, global debt was at 225 percent of global GDP in the first half of the year – most of this was in the private sector.

The Frenchman also warned against growing prices in bonds and other financial instruments.

"Looking at the asset markets as a whole, it's absolutely clear that we had such a long period of very low interest rates, such a long period of purchases through QEs in the various advanced economies, that it's not surprising that the prices of the financial assets went up," Trichet said.

"All of this is explainable, but, of course, the present level of some assets' prices calls again for vigilance and prudence and caution."

Earlier this week, a survey published by Bank of America Merrill Lynch showed that, despite the fact that investors think equities are too expensive, they keep purchasing them because they think they will become even more expensive.